9418 Ww. A. E. USSHER ON THE TRIASSIC 
cession doubtful. In La Manche gravels and sandstones seem to be 
generally uppermost. 
Commencing in the north of the district with Valognes as a 
starting-point, the succeeding sections will show how inconsiderable 
is the thickness of the Trias in that part of the area. 
Section I. (fig. 1). From Valognes by Huberville and St. Martin 
d Audouyille to Crasville-—The town of Valognes is situated on Infra- 
lias limestones, exposed in quarries in some places to a depth of 40 feet. 
The first valley, crossing the road along which the section is taken, 
exposes whitish sand under greenish marl, mottled with red, overlain 
by Infralias, which appears to be the subsoil nearly as far as the turn- 
ing to St. Germain-de-Tournebut. In quarries near Huberville the 
Pecten-valoniensis beds are present; the rock presents a somewhat 
concretionary structure and rubbly bedding; it is overlain by dilu- 
vium 10 feet thick, consisting of drab and brown sandy clay, with 
occasional quartzite pebbles and fragments of the subjacent rock. 
Another set of quarries, further east, show 5 feet of similar diluyium 
on 8 feet of Infralias, composed of :— 
1. Thin rubbly limestones overlain by diluvium. 
2. Whitish and grey limestones. 
3. Grey shaly clay and tough impure yellowish and grey lme- 
stones. 
The beds appear to be horizontal. Pecten valoniensis is present. 
The next valley toward St. Germain-de-Tournebut may have been 
cut through to the Trias, if traces of greenish and bluish-grey clay 
can be taken as evidence of the proximity of that formation. Near 
the turning to St. Germain-de-Tournebut, gravel of quartzite and 
erit pebbles in coarse yellowish-brown sand, apparently in part 
composed of flint, covers the surface ; toward St. Martin d’Audouville 
this gravel gives place to gravel of irregular quartzite and quartz 
pebbles, generally small, but occasionally of fair size, in coarse yel- 
lowish-brown sand, in parts of which the pebbles are very sparsely 
disseminated. ‘The distribution of these materials is as perfect an 
index of bedding as that exhibited by many of the pebble-bed sections 
in Devonshire. 
I regard the bedded gravel as Triassic, and that previously men- 
tioned as composed of redistributed material, for the following reasons: 
—First. Silurian quartzites are exposed at the surface not far to the 
southward, and pebbles of quartzite occur in the drifts covering the 
Infralias, which are probably represented by the first-mentioned 
gravel near St. Germain-de-Tournebut. Secondly. The bedded gravel 
occurs in a place where Trias might be expected ; for, had the Infra- 
lias continued beyond the turning to St. Germain-de-Tournebut, one 
would expect to find less quartzite and more local fragments in the 
overlying drifts. Thirdly. From the proximity of Silurian quart- 
zites the Triassic beds might naturally be expected to take the form 
of gravels, and the drift upon them to be largely composed of their 
redistributed materials, as if directly derived from the Silurian the 
pebbles would be less worn. 
By the Chemin Vicinal, south of St. Martin d’Audouyille, gravel 
